The time it takes for symptoms of anaphylaxis to develop depends on the cause.
If it was something you ate, such as peanuts, it can take anything from a few minutes to two hours. If it was something that entered your skin, such as a sting or an injection, it will usually take between five and 30 minutes.
Read more about the causes of anaphylaxis.
Allergic reactions can vary in severity. Sometimes they only involve mild itching or swelling, but in some people they can be severe and life-threatening.
Symptoms of anaphylaxis include:
- a red, raised, itchy skin rash (hives)
- swelling of certain body parts, particularly the face (angioedema)
- swelling in your throat and narrowing of your airways, which can cause breathing difficulties and wheezing
- nausea
- vomiting
- a sudden drop in blood pressure, which can make you feel faint and dizzy
- feeling like something terrible is going to happen
When to seek medical advice
If someone has the symptoms of anaphylaxis, they need urgent medical help, particularly if you know they have allergies.
You should immediately dial 999 for an ambulance.
